(1) Field of the Invention
The present invention relates to a semiconductor wafer positioning method for determining a handling position of a semiconductor wafer having a detection site such as a V notch or an orientation flat at a peripheral edge thereof based on positional information of the detection site, and relates to an apparatus using the method.
(2) Description of the Related Art
A semiconductor wafer (hereinafter, simply referred to as a “wafer”) is subjected to back surface processing performed by a mechanical method such as grinding or polishing, a chemical method using etching, or the like, so that the thickness thereof is reduced. When the wafer is processed by using such a method, a protective tape is joined to the wafer surface so as to protect the surface on which a wiring pattern has been formed. For the polished wafer on which the protective tape is joined, positional information of the peripheral edge is obtained in a process of being rotationally scanned in a state that the peripheral edge is interposed between a light source and a photoreception sensor. Based on the positional information, the center position of the wafer is obtained (see, for example, JP-A 08-279547 (1996)).
Further, at the same time as obtaining the center position of the wafer, positional information about the detection site such as a V notch or an orientation flat used for positioning is obtained, and based on the information, a handling position of the wafer is determined. That is, on the basis of the position of the detection site, a handling position is determined while considering a rotational direction about the wafer center axis when transported or joined and held from the wafer back surface to a ring frame via a supporting adhesive tape.
However, the conventional method involves the following problem.
Recently, a wafer is required to be thinner along with the rapid progress of application, so it is processed to be as thin as 150 μm or less. As a wafer becomes thinner, the rigidity of the wafer itself is reduced. Therefore, in order to make the wafer rigid, a protective tape made of a base material which is thick or hard material is joined to the wafer surface, for example. However, a protective tape joined so as to cover the whole surface of the wafer interrupts light transmitting a V notch portion for positioning formed in the peripheral edge of the substantially circular wafer. Therefore, the photoreception sensor cannot be received the projected light in the V notch portion
Further, there are protective tapes in which surface processing and coloring are performed and the thickness is increased, whereby some types thereof are less likely to transmit light.
In such a case, a detection site in the peripheral edge of the wafer can be detected easily by an image processing system utilizing an optical system such as a camera. However, there is a problem that it is difficult to incorporate an image processing system in a conventional apparatus. Further, since an image processing system is expensive, there is caused a disadvantage that a burden of the installment cost is large.